Q: What is platelet clumping? What is the inference of peripheral smear? I am a 58 years old man and my platelets are adequate but small clumps have been seen on the smear in the CBC report. The platelet count is 1.35 L.

A:Most haematology analysers count the number of platelets by sizing them. Cells larger than, or particles smaller than a particular size are disregarded by the platelet channel and not counted as platelets. There is a condition called pseudothrombocytopenia, spuriously low platelet count due to a laboratory artefact, in which the platelets clump together. In such instances the instrument does not count these clumps of platelets and gives the platelet count as factitiously low. This can be confirmed by examining a peripheral blood smear in which many clumps of platelets will be seen suggesting that the platelet count is normal. Sometimes, changing the anticoagulant in which the blood is collected from EDTA to citrate or heparin may solve the problem but rarely, platelets may clump on being exposed to any anticoagulant. If a platelet count is still required in such cases, a manual platelet count is done using finger-prick blood and directly collecting the blood into the diluting fluid. Pseudothrombocytopenia may also be seen in some patients who are taking certain drugs. The anticoagulant (or drug) affects the membrane of platelets causing a conformational change in them because of which they bind to non-specific circulating antibodies in the blood and clump together. The condition has no clinical significance other than scaring the treating physician.